The use of fibrous additives in road construction asphalt is common.
For instance, French Patent 26 76 436-A1 mentions the addition of polyacrylonitrile fiber 10-50 mm in length and 25-100.mu. in diameter to delay cracking.
German Patent 39 30 599-A mentions the addition of reinforcing fibers, normally polyacrylonitrile.
It is known to add steel fibers combined with acrylonitrile-based fibers to reduce the formation of ruts in bituminous pavements (La Construction, Nov. 8, 1991, Belgium). The product .RTM.Arbocel is known for use as a stabilizer for bituminous mixing partners based on fiber material. In the case of mastic asphalt, for example, the addition is preferably 0.3% by weight.
U. S. Pat. No. 4,663,370 describes the use of organic staple fibers, for example polyolefin fibers and polyester fibers. These fibers are added to the material which is applied as the new wear course in the repair of bituminous pavements. This is done to fill in and even out ruts and cracks. According to the invention, such a fiber use of 0.25-10% by weight is combined with up to 10% by weight of straight-chain, unsaturated fatty acid containing up to 30% by weight of resin as plasticizing aid, with up to 10% by weight of a customary inorganic addition, for example sand, and with a proportion of finely divided, high density polyester or polyolefin for adhesion improvement. The last component should have a particle diameter of not above 200.mu. and a length of not above 1.5 mm. This formulation is said to keep rut formation at elevated temperature and wash-out processes under control.
In the art of manufacturing bituminous pavements, it is known that the addition of a fiber material can inhibit the flow of the bitumen in the asphalt immediately after mixing, during transport and during incorporation. Specific fiber materials insure that the entire amount of binder required for the performance characteristics remains homogeneously dispersed. Bitumen runoff can lead to damage to the finished reinforcement, to the extent of complete destruction during use.
A further aspect is taken into account here:
The conservation of primary raw materials is of fundamental importance. If a comparable solution can be achieved by using secondary raw materials, this is preferable to the use of a primary raw material.
It may be specifically recalled that a recovered material whose starting materials are wastes based on polyester monofils ought to be found an advantageous use. Such polyester filaments are used for example in paper machines in the sheet formation region and at the dry end and also for various product filtrations, pressing operations and transport operations. Waste materials are produced in the manufacture of these filaments, in fabric making, in fabric setting, in making up and finally as product after the intended use.
Substantially clean product can flow back into man-made fiber production through remelting and additional treatment steps, for specific articles. However, this is not solution for the entire amount available on the market and for the product after its intended use. Here the only solutions on offer remain landfilling and incineration with recovery of thermal energy. On the other hand, the number of companies involved in the manufacture of such products and the number of users are limited, so that specific collection of such waste materials is possible.
Hereinafter it will be shown that these various themes can be advantageously combined in the creation of a novel product having a favorable combination of properties.